Continuously variable transmission

ABSTRACT

Disclosed embodiments are directed to components, subassemblies, systems, and/or methods for continuously variable transmissions (CVT). In one embodiment, a CVT has a number of spherical planets in contact with an idler. Various idler assemblies can be used to facilitate to improve durability, fatigue life, and efficiency of a CVT. In one embodiment, the idler assembly has two rolling elements having contact surfaces that are angled with respect to a longitudinal axis of the CVT. In some embodiments, a bearing is operably coupled between the first and second rolling elements. The bearing is configured to balance axial force between the first and second rolling elements. In one embodiment, the bearing is a ball bearing. In another embodiment, the bearing is an angular contact bearing. In yet other embodiments, needle roller bearings are employed. 
     19309810

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/288,711, filed Nov. 3, 2011 and scheduled to issue on Nov. 18, 2014as U.S. Pat. No. 8,888,643, which claims the benefit of U.S. ProvisionalApplication No. 61/412,290, filed on Nov. 10, 2010. The disclosures ofall of the above-referenced prior applications, publications, andpatents are considered part of the disclosure of this application, andare incorporated by reference herein in their entirety.

BACKGROUND

1. Field of the Invention

This disclosure relates generally to mechanical and/orelectro-mechanical power modulation devices and methods. Moreparticularly, this disclosure relates to continuously and/or infinitelyvariable, planetary power modulating devices, and methods for modulatingpower flow in a power train or drive, such as power flow from a primemover to one or more auxiliary or driven devices.

2. Description of the Related Art

Continuously variable transmissions (CVT) having spherical planets suchas those generally described in U.S. Pat. No. 7,011,600 to Miller et al,U.S. Pat. No. 5,236,403 to Schievelbusch, or U.S. Pat. No. 2,469,653 toKopp, typically have a rotatable support member or an idler component incontact with each spherical planet. In some systems, the idler is agenerally cylindrical member located radially inward of each sphericalplanet. During operation of these types of CVTs, the spherical planetsexert forces on the idler that generate high stress at the locationcontacting the spherical planets. The type of stress is commonly knownas a hertzian contact stress. Fatigue life and/or durability of arolling element, such as an idler, is a function of the hertzian stressexerted on the rolling element over time. High stress exerted on theidler component leads to lower fatigue life and lower efficiencyperformance of the CVT.

Thus, there exists a continuing need for devices and methods to improvethe fatigue life of idler components. Embodiments of power modulatingdevices and/or drivetrains described below address one or more of theseneeds.

SUMMARY OF THE INVENTION

The systems and methods herein described have several features, nosingle one of which is solely responsible for its desirable attributes.Without limiting the scope as expressed by the claims that follow, itsmore prominent features will now be discussed briefly. After consideringthis discussion, and particularly after reading the section entitled“Detailed Description of Certain Embodiments” one will understand howthe features of the system and methods provide several advantages overtraditional systems and methods.

One aspect of the disclosure relates to a continuously variabletransmission (CVT) having a longitudinal axis. In one embodiment, theCVT includes a group of spherical traction planets. Each traction planethas an axle about which it rotates. The axle is configured to tilt withrespect to the longitudinal axis. The CVT includes an idler assembly incontact with each of the traction planets. In one embodiment, the idlerassembly is located radially inward of each of the traction planets. Theidler assembly has first and second rolling elements. The first andsecond rolling elements are configured to rotate at different speedscorresponding to the tilt of the traction planets.

Another aspect of the disclosure relates to a continuously variabletransmission (CVT) having a group of traction planet assemblies arrangedangularly about a longitudinal axis of the CVT. In one embodiment, theCVT includes a first carrier coupled to the each of the traction planetassemblies. The first carrier is provided with a number of radiallyoffset slots. The first carrier is configured to guide the tractionplanet assemblies. The CVT also includes an idler assembly in contactwith each of the traction planets. The idler assembly is locatedradially inward of each traction planet. The idler assembly has firstand second rolling elements.

Yet another aspect of the disclosure relates to a continuously variableaccessory drive system (CVAD). In one embodiment, the CVAD has a shaftarranged along a longitudinal axis of the CVAD. The CVAD includes afirst traction ring coaxial about the longitudinal axis. The CVAD alsoincludes a group of traction planets in contact with the first tractionring. The traction planets are arranged angularly about the longitudinalaxis. In one embodiment, the CVAD includes a carrier operably coupled tothe each of the traction planets. The carrier is provided with a numberof radially offset guide slots. The CVAD also includes an idler assemblyin contact with each of the traction planets. The idler assembly islocated radially inward of each traction planet. The idler assembly hasfirst and second rolling elements. The CVAD includes an alternatorcoupled to the shaft.

One aspect of the invention relates to an idler assembly for acontinuously variable transmission (CVT) having a group of tractionplanet assemblies arranged about a longitudinal axis. Each tractionplanet assembly is operably coupled to a carrier having a number ofradially offset guide slots. In one embodiment, the idler assemblyincludes first and second rolling elements in contact with each tractionplanet assembly. The first and second rolling elements are locatedradially inward of each traction planet assembly. The idler assemblyalso includes a bearing operably coupling the first rolling element tothe second rolling element. The bearing is configured to balance axialforce between the first and second rolling elements.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a cross-sectional view of an embodiment of a continuouslyvariable accessory drive (CVAD) having a skew control system.

FIG. 2 is a partially cross-sectional perspective view of certaincomponents of the CVAD of FIG. 1.

FIG. 3 is a cross-sectional exploded view of an idler assembly that canbe used with the CVAD of FIG. 1.

FIG. 4 is a plan view of a carrier that can be used with the CVAD ofFIG. 1.

FIG. 5 is a plan view of a carrier that can be used with the CVAD ofFIG. 1.

FIG. 6 is a diagram of one embodiment of an idler assembly that can beused with the CVAD of FIG. 1.

FIG. 7 is a diagram of one embodiment of an idler assembly that can beused with the CVAD of FIG. 1.

FIG. 8 is a diagram of one embodiment of an idler assembly that can beused with the CVAD of FIG. 1.

DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS

The preferred embodiments will be described now with reference to theaccompanying figures, wherein like numerals refer to like elementsthroughout. The terminology used in the descriptions below is not to beinterpreted in any limited or restrictive manner simply because it isused in conjunction with detailed descriptions of certain specificembodiments. Furthermore, embodiments of the disclosure can includeseveral novel features, no single one of which is solely responsible forits desirable attributes or which is essential to practicing theembodiments described. Certain CVT embodiments described here aregenerally related to the type disclosed in U.S. Pat. Nos. 6,241,636;6,419,608; 6,689,012; 7,011,600; 7,166,052; U.S. patent application Ser.Nos. 11/243,484; Ser. No. 11/543,311; Ser. No. 12/198,402, Ser. No.12/251,325; and Patent Cooperation Treaty patent applicationsPCT/US2007/023315, PCT/IB2006/054911, PCT/US2008/068929, andPCT/US2007/023315, PCT/US2008/074496. The entire disclosures of each ofthese patents and patent applicationsare hereby incorporated herein byreference.

As used here, the terms “operationally connected,” “operationallycoupled,” “operationally linked,” “operably connected,” “operablycoupled,” “operably linked,” and like terms, refer to a relationship(mechanical, linkage, coupling, etc.) between elements whereby operationof one element results in a corresponding, following, or simultaneousoperation or actuation of a second element. It is noted that in usingsaid terms to describe certain embodiments, specific structures ormechanisms that link or couple the elements are typically described.However, unless otherwise specifically stated, when one of said terms isused, the term indicates that the actual linkage or coupling may take avariety of forms, which in certain instances will be readily apparent toa person of ordinary skill in the relevant technology. For descriptionpurposes, the term “axial” as used here refers to a direction orposition along an axis that is parallel to a main or longitudinal axisof a transmission or variator. The term “radial” is used here toindicate a direction or position that is perpendicular relative to alongitudinal axis of a transmission or variator.

It should be noted that reference herein to “traction” does not excludeapplications where the dominant or exclusive mode of power transfer isthrough “friction.” Without attempting to establish a categoricaldifference between traction and friction drives here, generally thesemay be understood as different regimes of power transfer. Tractiondrives usually involve the transfer of power between two elements byshear forces in a thin fluid layer trapped between the elements. Thefluids used in these applications usually exhibit traction coefficientsgreater than conventional mineral oils. The traction coefficient (μ)represents the maximum available traction forces which would beavailable at the interfaces of the contacting components and is ameasure of the maximum available drive torque. Typically, frictiondrives generally relate to transferring power between two elements byfrictional forces between the elements. For the purposes of thisdisclosure, it should be understood that the CVTs described here mayoperate in both tractive and frictional applications. For example, inthe embodiment where a CVT is used for a bicycle application, the CVTcan operate at times as a friction drive and at other times as atraction drive, depending on the torque and speed conditions presentduring operation.

Embodiments disclosed here are related to the control of a variatorand/or a CVT using generally spherical planets each having a tiltableaxis of rotation that can be adjusted to achieve a desired ratio ofinput speed to output speed during operation. In some embodiments,adjustment of said axis of rotation involves angular displacement of theplanet axis in a first plane in order to achieve an angular adjustmentof the planet axis in a second plane, wherein the second plane issubstantially perpendicular to the first plane. The angular displacementin the first plane is referred to here as “skew,” “skew angle,” and/or“skew condition”. For discussion purposes, the first plane is generallyparallel to a longitudinal axis of the variator and/or the CVT. Thesecond plane can be generally perpendicular to the longitudinal axis. Inone embodiment, a control system coordinates the use of a skew angle togenerate forces between certain contacting components in the variatorthat will tilt the planet axis of rotation substantially in the secondplane. The tilting of the planet axis of rotation adjusts the speedratio of the variator. The aforementioned skew angle, or skew condition,can be applied in a plane substantially perpendicular to the plane ofthe page of FIG. 1, for example. Embodiments of transmissions employingcertain skew control systems for attaining a desired speed ratio of avariator will be discussed.

One aspect of the torque/speed regulating devices disclosed here relatesto drive systems wherein a prime mover drives various driven devices. Inthis sense, regulating is used to mean varying the transmission ratio tovary the torque or speed of the power being provided to the accessory tocorrespond with the operating requirements of the accessory being drivenfrom the CVT. The prime mover can be, for example, an electrical motorand/or an internal combustion engine. For purposes of description here,an accessory includes any machine or device that can be powered by aprime mover. For purposes of illustration and not limitation, saidmachine or device can be a power takeoff device (PTO), pump, compressor,generator, auxiliary electric motor, etc. Accessory devices configuredto be driven by a prime mover may also include alternators, water pumps,power steering pumps, fuel pumps, oil pumps, air conditioningcompressors, cooling fans, superchargers, turbochargers and any otherdevice that is typically powered by an automobile engine. As previouslystated, usually, the speed of a prime mover varies as the speed or powerrequirements change; however, in many cases the accessories operateoptimally at a given, substantially constant speed. Embodiments of thetorque/speed regulating devices disclosed here can be used to controlthe speed of the power delivered to the accessories powered by a primemover.

For example, in some embodiments, the speed regulators disclosed herecan be used to control the speed of automotive accessories driven by apulley attached to the crankshaft of an automotive engine. Usually,accessories must perform suitably both when the engine idles at lowspeed and when the engine runs at high speed. Often accessories operateoptimally at one speed and suffer from reduced efficiency at otherspeeds. Additionally, the accessory design is compromised by the need toperform over a large speed range rather than an optimized narrow speedrange. In many cases when the engine runs at a speed other than lowspeed, accessories consume excess power and, thereby, reduce vehiclefuel economy. The power drain caused by the accessories also reduces theengine's ability to power the vehicle, necessitating a larger engine insome cases.

In other situations, inventive embodiments of the torque/speedregulating devices disclosed here can be used to decrease or increasespeed and/or torque delivered to the accessories for achieving optimalsystem performance. In certain situations, embodiments of thetorque/speed regulating devices disclosed here can be used to increasespeed to the accessories when the prime mover runs at low speed and todecrease speed to the accessories when the prime mover runs at highspeed. Thus, the design and operation of accessories can be optimized byallowing the accessories to operate at one, substantially favorablespeed, and the accessories need not be made larger than necessary toprovide sufficient performance at low speeds. For example, theembodiments of the torque/speed regulating devices disclosed here canenable more power to be extracted from an accessory such as analternator when the prime mover or engine is running at low idle speed.The accessories can also be made smaller because the torque/speedregulating devices can reduce speed to the accessories when the primemover runs at high speed, reducing the stress load the accessories mustwithstand at high rpm. Because the accessories are not subjected to highspeeds, their expected service life can increase substantially. In somecases, smoother vehicle operation results because the accessories do nothave to run at low or high speed. Further, a vehicle can operate morequietly at high speed because the accessories run at a lower speed.

Embodiments of a continuously variable transmission (CVT), andcomponents and subassemblies thereof, will be described now withreference to FIGS. 1-8. FIG. 1 shows a CVT 10 that can be used in manyapplications including, but not limited to, continuously variableaccessory drives, human powered vehicles (for example, bicycles), lightelectrical vehicles, hybrid human-, electric-, or internal combustionpowered vehicles, industrial equipment, wind turbines, etc. Anytechnical application that requires modulation of mechanical powertransfer between a power input and a power sink (for example, a load)can implement embodiments of the CVT 10 in its power train.

Referring now to FIGS. 1-3, in one embodiment the CVT 10 is providedwith a number of traction planet assemblies 12 arranged radially about alongitudinal axis 14. Each traction planet assembly 12 includes aspherical traction planet 16 configured to rotate about a planet axle18. The planet axle 18 can tilt with respect to the longitudinal axis14. Ends of the planet axle 18 can be coupled to first and secondcarriers 20, 21. In one embodiment, the first and second carriers 20, 21are adapted to rotate with respect to each other. The CVT 10 can beprovided with a first traction ring assembly 22 in contact with each ofthe traction planets 16. In one embodiment, the first traction ringassembly 22 is adapted to receive a power input from a drive pulley 23.The CVT 10 can be provided with a second traction ring assembly 24 incontact with each of the traction planets 16. In one embodiment, thefirst and second traction ring assemblies 22, 24 are each provided witha traction ring 26 and an axial force generator assembly 28. In someembodiments, the axial force generator assembly 28 can include a tonewheel configured to cooperate with, for example, a speed sensor (notshown). The CVT 10 is provided with a shaft 30 arranged along thelongitudinal axis 14. The shaft 30 can be configured to transfer powerto an accessory (not shown), such as an alternator. The shaft 30 isconfigured to drive, among other things, a pump 32. In one embodiment,the pump 32 is a gerotor type pump having an inner driven gear 31coupled to an outer gear 33. The inner driven gear 31 is coupled to theshaft 30. The pump 32 is in fluid communication with a lubricantmanifold 34. The lubricant manifold 34 is attached to a pump cavity 35.The pump cavity 35 and the lubricant manifold 34 substantially enclosethe pump 32. The pump cavity 35 is coupled to a housing 36. The housing36 substantially encloses and supports components of the CVT 10. Thelubricant manifold 34, the pump cavity 35, and the shaft 30 are providedwith a number of passages that are appropriately arranged to introduce alubricant from a reservoir (not shown) into the pump 32 and deliver thelubricant to internal components of the CVT 10. In one embodiment, thereservoir is integral with the housing 36. In some embodiments, thereservoir can be remotely located.

In one embodiment, the CVT 10 is provided with an idler assembly 40arranged radially inward of, and in contact with, each of the tractionplanets 16. The idler assembly 40 couples to a sleeve 42. The sleeve 42is coaxial with, and surrounds, the shaft 30. In some embodiments, thesleeve 42 can be integral to the shaft 30. The sleeve 42 can be made ofa different material than the shaft 30. For example, the sleeve 42 canbe made of a material that has properties appropriate for a bearing raceor a journal. In one embodiment, the idler assembly 40 includes a firstrolling element 44 operably coupled to a second rolling element 46. Thefirst rolling element 44 is radially supported on the sleeve 42 by abearing 48. The bearing 48 can be a needle roller bearing, for example.The second rolling element 46 is radially supported by a bearing 50. Thebearing 50 can be a needle roller bearing, for example. The secondrolling element 46 is supported in the axial direction by a bearing 52.The bearing 52 can be a ball bearing, for example. The bearing 52 iscoupled to a race 53. The race 53 is attached to the first rollingelement 44 with, for example, a clip 54. The bearing 52 is positioned ina manner to balance the axial force applied to the first rolling element44 with the axial force applied to the second rolling element 46.

During operation of the CVT 10, the first and second rolling elements44, 46 rotate about the longitudinal axis 14. The first and secondrolling elements 44, 46 each rotate at a speed corresponding to the tiltangle of the planet axle 18 with respect to the longitudinal axle 14.Under some operating conditions, for example when the planet axle 18 issubstantially parallel to the longitudinal axis 14, the speed of thefirst rolling element 44 is substantially equal to the speed of thesecond rolling element 46. Under other operating conditions, the speedof the first rolling element 44 can be higher than the speed of thesecond rolling element 46. Under yet other operating conditions, thespeed of the first rolling element 44 can be lower than the speed of thesecond rolling element 46. During operation of the CVT 10, thedifference in speed between the first and second rolling elements 44, 46is transmitted to the bearing 52. This is advantageous since the speeddifference between the first and second rolling elements 44, 46 istypically small. It is well known that parasitic losses from bearingsare related to the speed and load at which a bearing operates. Since thebearing 52 typically operates under relatively high axial loads,reducing the speed at which the bearing 52 operates serves to reduce theparasitic loss of the bearing 52.

Referring now specifically to FIG. 3, in one embodiment the firstrolling element 44 is a generally cylindrical body having a ring 56formed on one end. The first rolling element 44 is provided with ashoulder 58 extending from the ring 56. The shoulder 58 has a number ofholes 60 arranged radially about the circumference of the cylindricalbody. The holes 60 can facilitate the flow of lubricant to, for example,the bearing 50. In some embodiments, the holes 60 facilitate the flow oflubricant to the contacting surfaces between the traction planets 16 andthe first and second rolling elements 44, 46. The shoulder 58 isprovided with a groove 62 formed on the outer periphery of thecylindrical body. The groove 62 is adapted to receive the clip 54. Thefirst rolling element 44 is provided with grooves 64 on the innercircumference of the cylindrical body. The grooves 64 are adapted toreceive, for example, clips 66 (FIG. 2). The clips 66 facilitate theretention of the bearing 48 (FIG. 2) with respect to the first rollingelement 44.

Turning now to FIG. 4, in one embodiment the first carrier 20 is asubstantially bowl-shaped body having a central bore 72. The bowl-shapedbody can be provided with a number of guide slots 74 arranged angularlyabout the central bore 72. The guide slots 74 are aligned with a radialconstruction line 76 when viewed in the plane of the page of FIG. 4. Theguide slots 74 are adapted to receive one end of the planet axle 18. Thebowl-shaped body is provided with a flange 77 formed about the outerperiphery. The flange 77 can be adapted to attach to the housing 36.

Referring now to FIG. 5, in one embodiment the second carrier 21 is asubstantially bowl-shaped body having a central bore 82. The bowl-shapedbody can be provided with a number of guide slots 84 arranged angularlyabout the central bore 82. Each guide slot 84 is sized to accommodatethe coupling of the second carrier 21 to the planet axle 18. The guideslots 84 are angularly offset from the radial construction line 76 whenviewed in the plane of the page of FIG. 5. The angular offset can beapproximated by an angle 88. The angle 88 is formed between the radialconstruction line 76 and a construction line 90. The construction line90 substantially bisects the guide slot 84 when viewed in the plane ofthe page of FIG. 5. In some embodiments, the angle 88 is between 3degrees and 45 degrees. A low angle 88 would provide faster shift ratesin a given application but rotation of the carrier 21 must be controlledover a very small range. A high angle 88 would provide slower shiftrates in a given application but rotation of carrier 21 would becontrolled over a larger range. In effect, a low angle 88 produces ahighly responsive transmission ratio change but potentially moredifficult to control or stabilize, while a high angle can be lessresponsive in transmission ratio change but easy to control bycomparison. In some embodiments, where it is desirable to have highspeed, fast shift rates, the angle 88 can be, for example, 10 degrees.In other embodiments, where it is desirable to have slower speed,precise control of transmission ratio, the angle 88 can be about 30degrees. However, the said values of the angle 88 are provided as anillustrative example, and the angle 88 can be varied in any manner adesigner desires. In some embodiments, the angle 88 can be any angle inthe range of 10 to 25 degrees including any angle in between orfractions thereof. For example, the angle can be 10, 11, 12, 13, 14, 15,16, 17, 18, 19, 20, 21, 22, 23, 24, 25, or any portion thereof. In otherembodiments, the angle 88 can be 20 degrees. In one embodiment, theguide slots 84 can be arranged so that the construction line 90 isradially offset from a construction line 91 by a distance 92. Theconstruction line 91 is parallel to the construction line 90 andintersects the center of the bowl-shaped body.

In one embodiment, the second carrier 21 is coupled to a clevis 94. Theclevis 94 can be accessed through an opening (not shown) in the housing36 to facilitate the coupling of the clevis 94 to an actuator (notshown). During operation of the CVT 10, a change in transmission ratiocan be accomplished by rotating the second carrier 21 with respect tothe first carrier 20. A rotation of the second carrier 21 can beaccomplished by moving the clevis 94 with the actuator.

Referring now to FIG. 6, in one embodiment an idler assembly 100includes a spherical traction planet 101. The spherical traction planet101 can be provided with a tillable axis of rotation (not shown). Theidler assembly 100 includes first and second rolling elements 102, 103,respectively. In some embodiments, the first rolling element 102 can becoupled to at least one bearing 104 at a radially inward location. Inother embodiments, the bearing 104 is not used. The second rollingelement 103 can be coupled to at least one bearing 105 at a radiallyinward location. The bearing 105 is supported by the first rollingelement 102. The second rolling element 103 can be axially coupled tothe first rolling element 102 with a bearing 106. In some embodiments,the bearing 106 can be an angular contact bearing, in such cases thebearing 105 can be removed. The bearing 106 is coupled to a shoulder 107attached to the first rolling element 102. In one embodiment, theshoulder 107 is integral to the first rolling element 102. In otherembodiments, the shoulder 107 is a separate component that is fixedlyattached to the first rolling element 102. Each of the first and secondrolling elements 102, 103 are provided with contact surfaces 109, 110,respectively. The contact surfaces 109, 110 are in contact with thetraction planet 101. The contact surfaces 109, 110 are angled withrespect to a longitudinal axis 111 at an angle 112 when viewed in theplane of the page of FIG. 6. In some embodiments, the angle 112 can beany angle in the range of 0 to 45 degrees including any angle in betweenor fractions thereof. For example, the angle can be 0, 1, 2, 3, 4, 5, 6,7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25,26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43,44, 45 or any portion thereof. In other embodiments, the angle 112 canbe 10 degrees. In some embodiments, the first rolling element 102 isconfigured to receive an input power.

Passing now to FIG. 7, in one embodiment an idler assembly 120 caninclude first and second rolling elements 121, 122, respectively. Thefirst and second rolling elements 121, 122 are each coupled to a bearing123. The bearings 123 can be attached to a sleeve 124 with, for example,clips 125. The first and second rolling elements 121, 122 are eachprovided with a contact surface 126. The contact surfaces 126 are incontact with the traction planet 101. The contact surfaces 126 areformed at the angle 112 relative to the longitudinal axis 111 whenviewed in the plane of the page of FIG. 7.

Referring now to FIG. 8, in one embodiment an idler assembly 130 caninclude first and second rolling elements 132, 133, respectively. Thefirst and second rolling elements 132, 133 are each coupling to abearing 136. The bearing 136 can be provided with a cage 137. The firstrolling element 132 has an extension 134. The extension 134 coupled tothe bearing 136. In one embodiment, the bearing 136 is an angularcontact bearing. The first rolling element 132 is provided with acontact surface 139. The contact surface 139 is in contact with thetraction planet 101. The second rolling element 133 is provided with acontact surface 140. The contact surfaces 139, 140 are formed at theangle 112 relative to the longitudinal axis 111 when viewed in the planeof the page of FIG. 8.

It should be noted that the description above has provided dimensionsfor certain components or subassemblies. The mentioned dimensions, orranges of dimensions, are provided in order to comply as best aspossible with certain legal requirements, such as best mode. However,the scope of the embodiments described herein are to be determinedsolely by the language of the claims, and consequently, none of thementioned dimensions is to be considered limiting on the embodiments,except in so far as any one claim makes a specified dimension, or rangeof thereof, a feature of the claim.

The foregoing description details certain embodiments of the disclosure.It will be appreciated, however, that no matter how detailed theforegoing appears in text, the disclosure can be practiced in many ways.As is also stated above, it should be noted that the use of particularterminology when describing certain features or aspects of thedisclosure should not be taken to imply that the terminology is beingre-defined herein to be restricted to including any specificcharacteristics of the features or aspects of the disclosure with whichthat terminology is associated.

What we claim is:
 1. An idler for a continuously variable transmission(CVT) having a plurality of traction planet assemblies arranged about alongitudinal axis, each traction planet assembly operably coupled to acarrier having a plurality of radially offset guide slots, the idlerassembly comprising: a first rolling element rotatable about an axis ata first speed corresponding to a tilt angle of a planet axle relative tothe longitudinal axis; a second rolling element rotatable about the axisat a second speed corresponding to the tilt angle of a planet axlerelative to the longitudinal axis; and a first bearing interposedbetween the first rolling element and the second rolling element.
 2. Theidler assembly of claim 1, wherein each of the first rolling element andthe second rolling element comprises a first surface angled for contactwith a traction planet and a second surface angled less than the firstangle.
 3. The idler assembly of claim 2, wherein the first angle is inthe range between 0 and 45 degrees.
 4. The idler assembly of claim 3,wherein the first angle is in the range between 0 and 10 degrees.
 5. Theidler assembly of claim 2, wherein the second rolling element is axiallycoupled to the first rolling element with a second bearing.
 6. The idlerassembly of claim 5, wherein the second bearing is coupled to a shoulderof the first rolling element.
 7. The idler assembly of claim 1, furthercomprising at least one bearing positioned radially inward of the firstrolling element.